Cooling apparatus



July 27, 1937. E. R. WOLFERT 2,088,254

I COOLING APPARATUS Filed Dec. 14, 1953 HYG' WITNESSES. INVENTOR W EDWARUR.WOLFERT BY 2W Patented July 27, 1937 COOLING APPARATUS Edward R. Wolfert, Wilkinsburg, 1a., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania ApplicationDecember 14, 1933, Serial No. 702,387

6 Claims. (01. 62-129) My invention relates tocooling or refrigerating apparatus, more particularly to an evaporator of the dry expansion type for cooling air or other fluid, and-it has for an object to provide an improved evaporator.

It is an object of my invention to provide an evaporator for cooling a fluid, having an improved arrangement of refrigerant passage with respect to flow of the fluid being cooled.

It is another object of my invention to 'utilize the heat-transfersurfaces of the evaporator in the most efilcient manner.

A further object. is to provide a more nearly uniform temperature difference between the refrlgerant and the fluid being cooled, and therefore, a higher mean effective temperature difference.

In accordance with my invention, I provide an evaporator of the so-called dry expansion" type. having a passage in which refrigerant flows in the same direction as the fluid being cooled, for the first portion of its path, and then flows in the opposite direction.

The utility of this arrangement will be understood from a consideration of the following: A pressure drop of the refrigerant is required to force the same through the passages, that is, the pressure of the refrigerant is highest at the inlet end and decreases toward the outlet end. The temperature of the refrigerant also decreases from the inlet toward the outlet end, as long as it is a mixture of liquid and gas. By placing the inlet end toward the incoming fluid to be cooled, the warmest portion of the latter is brought into heat-exchanging relation with the warmest refrigerant, and successively cooler portions of the fluid are brought into successively cooler portions of the refrigerant, whereby a more nearly uniform temperature difference is provided, and, consequently, more cooling for a given amount of cooling surface.

When the refrigerant'is completely evaporated, it issuperheated upon further addition of heat, its temperature increasing instead of decreasing. I, therefore, reverse the direction of flow as near as practical to the point where evaporation is completed, causing the refrigerant ,to flow in the direction opposite to that of the fluid being the well-known counterflow arrangement.

The above and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 is a diagrammatic view of refrigerating apparatus embodying my novel evaporator, which is shown in end elevation, partly in section, as seen along the line II of Fig. 2; and

Fig. 2 is a plan view of the evaporator. Referring to the drawing in detail, I show an evaporator Ill supplied with liquid refrigerant by a refrigerating unit l2, which may be of conventional design so far as the present invention is concerned. As shown, the refrigerating unit l2 comprises a. compressor l3 driven by a motor It. The compressor receives vaporous refrigerant through a suction conduit M and the compressed refrigerant is conveyed through a conduit l5 to a condenser is. A fan l1, driven by the motor I4, provides circulation of air or other cooling fluid through the condenser IS. The condensed refrigerant is conveyed to th evaporator through a/conduit l8.

The evaporator i0 is designed for circulation of air, or other fluid to be cooled, in a given direction through the evaporator. In the present embodiment, I provide one or more blowers l9 which effect circulation of air through the evaporator in the direction indicated by the arrows A in the several figures, which is to the left in Fig. 1. The evaporator III has a-casing 20, which has top, bottom and end walls but is open on the two sides through which the air passes into and out of the casing, as shown in the right hand end portion of Fig. 2. The evaporator l0 further comprises a bank or plurality of coils 2| therein which are arranged in parallel relation with respect to air flow, that is, they are arranged in superimposed relation as shown in Fig. 1, so that each coil is subjected to the same air temperatures and the action of the several coils is substantially identical. Each coil has an inlet 22 receiving liquid refrigerant from the conduit [8 through a flow resistance or capillary tube 23. The coil comprises tubes or turns 24, 25 and 26 arranged in a, horizontal plane, parallel to the direction of air flow, from the air inlet toward the air outlet; and further tubes or turns 21, 28, 29 and 30, arranged in an adjacent parallel plane in the reverse order, that is, from the air outlet toward the air inlet, and preferably in staggered relation to the flrst tubes. The latter four tubes are preferably below the first three tubes, so that the flow of liquid refrigerant from the tube 26 to the tube 21 is assisted by gravity. The last tube or turn 30 of each coil is connected through the outlet end 3! to a suction manifold 32, connected to the suction conduit I 4'. nected at their ends by reverse bends 33 disposed in a bracket 3 carried by the end wall 35 of the evaporator casing for supporting the coils in the evaporator.

In the operation of the above described apparatus, refrigerant is compressed by the compressor l3 and condensed by the condenser IS in the usual manner. The condensed refrigerant is distributed to the several coils, in this case, preferably in equal portions, by the capillary tubes 23. Since the coils 2i provide relatively long and narrow passages for refrigerant, an appreciable pressure drop or pressure difference is required to force the refrigerant through the coils with suflicient velocity. As an example, using dichlorodifluoromethane as refrigerant, the pressure at the inlet end may be assumed to be 40.7 lbs. per square inch and the pressure at the'outlet end 35 lbs. per square inch, providing a pressure drop of 5.7 lbs. per square inch. Also assume 10 superheating of the refrigerant vapor discharged at the outlet of the coil. In this case, then, the refrigerant entering the coil at the inlet end would have a temperature of 44 F. and

at some point in the evaporator near the outlet end, where all the refrigerant has been evaporated, the temperature will, be about 38 F. The temperature of the refrigerant vapor at the outlet end would then be about 48 F.

It is desirable to have the point at which all of the liquid is vaporized, at which point the temperature is at a. minimum, as near to the air outlet as possible, but in a practical construction, such as shown in Figs. 1 and 2, embodying substantially the same number of tubes in the two rows of each coil, this point may be somewhat spaced from the outlet end, for example, this point may occur in the tube 28 or possibly in the tube 29. However, the coolest region of each coil is adjacent the air outlet end while the warmer regions at the ends of each coil are adjacent the air inlet. Also, the tubes nearest the air outlet are at nearly the coolest temperature. The tubes adjacent the inlet, that is, tubes 24 and 25, contain the highest pressure and, therefore, the highest temperature of the refrigerant.

Being arranged adjacent the air inlet they are in heat exchange relation with the warmest portions of the air, that is, the incoming air. As the refrigerant continues in its flow through the coil toward the air outlet, its pressure and temperature decrease, and it comes into contact with cooler portions of the air, that is, the air which has been partially cooled adjacent the air inlet and which is about to leave the evaporator. When the refrigerant has been completely evaporated, it is no longer capable of absorbing heat by evaporation, so that the addition of further heat increases the temperature of the refrigerant. The refrigerant then flows toward the air inlet so to be in heat exchange relation with warmer air, that is, in counter-flow relation, and providing a more uniform difference between temperatures of the air and refrigerant.

It will be seen from the above description that I have provided an evaporator wherein a nearly uniform temperature difference is provided. The portion of each coil, adjacent the inlet end, containing a mixture of liquid and gaseous refrigerant provides for flow of refrigerant in the same direction as the flow of air, while the portion adjacent the outlet end provides for flow of the The successive turns of each coil are congaseous refrigerant in a direction opposite to the flow of air. It will be noted that I have provided one more tube in the second or lower row of each coil than in the upper row, the reason for this being that the heat absorbing capacity of the vaporous refrigerant is less than the liquid refrigerant.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is: I g

1. An evaporatorv for air cooling comprising a casing having two opposed side walls and two opposed end walls and being open on the two remaining opposed sides for the passage of air therethrough,'and a plurality of coils, each coil comprising a plurality of tubes or turns extending between the end walls of the casing, the tubes of each coil being disposed substantially in two adjacent rows parallel to said side walls and connected so that refrigerant flows through the tubes of one row successively from one open side to the other open side and then through the tubes of the adjacent row successively from the last-mentioned open side to said one open side,'

said coils being arranged in a bank or row extending from one side wall to the other so that the air flows over said coils in parallel, the evaporator being arranged for flow of refrigerant through the several coils in parallel.

, 2. An evaporator for air cooling comprising a. casing having two opposed side walls and two opposed end walls and being open on the two remaining opposed sides for the passage of air therethrough, a plurality of coils, each coil comprising a plurality of tubes or turns extending between the end walls of the casing, the tubes of each coil being disposed substantially in two adjacent rows parallel to said side walls and connected so that refrigerant flows through the tubes of one row successively from one open side to the other open side and then through the tubes 1 of the adjacent row successively from the lastmentioned open side to said one open side, said coils. being arranged in a bank or row extending from one side wall to the other so that the air flows over said coils in parallel, means for supplying refrigerant in parallel in substantially equal amounts to the first tube of the several coils, and an outlet or suction header connected in parallel to the last tube of each coil.

3. In air cooling apparatus, the combination of a bank of coils, each coil having an inlet and an outlet at one side of said bank and comprising tubes or turns arranged and connected so that refrigerant flows through successive tubes from the inlet on said one side to the opposite side of the bank and then back to the outlet on said one side, means for effecting forced circulation of air over said coils. in parallel from said one side to said opposite side, means for supplying vaporizable liquid refrigerant to the inlet of each coil, and means for withdrawing yaporized refrigerant from the outlet of each coil and 'for effecting complete vaporization of the liquid refrigerant before the refrigerant completes its passage through the coil, whereby the tubes adjacent the inlet contain liquid refrigerant decreasing in temperature in the direction I the unit and comprising tubes or turns arranged then back to the outlet end on said one side, the

evaporator unit being constructed and arranged .for flow of air over said coils in parallel from said one side to said opposite side, means for distributing a vaporizable liquid refrigerant from a'common source in substantially equal .p rtions to the inlet ends of the several coils, and a common discharge header connected to the outlet ends of the several coils.

5. An evaporator unit for cooling air comprising a plurality of coils, a common supporting structure for said coils, each coil having its inlet end and its .outlet endv at one side of the unit and comprising tubes or turns arranged and connected so that refrigerant flows through successive tubes from the inlet end on saidone side to the opposite side of said unit and then back to the outlet end. on said one side, the evaporator unit being constructed and arranged for flow of air over said coils in parallel from said one side to said'opposite side, means for distributing a vaporizable liquid refrigerant from a common source to the inlet ends of the sev:- eral coils, and a common discharge header connected to the outlet ends of the several coils.

6. In air cooling apparatus, .the combination of an evaporator unit comprising a plurality of coils and a common supporting structure for said coils, each coil having an inlet and an outlet at one side of said unit and comprising tubes or turns arranged and connected so that refrigerant flows through successive tubes from the inlet on said one side to the opposite side-of the unit and. then back to the outlet on said one side, means for effecting forced circulation of air over said coils in parallel from said one side to said opposite side, a common discharge header connected to the outlet ends of the several coils, a compressor having its inlet connected to the discharge header for withdrawing vaporized refrigerant from said coils and compressingv the same, means for condensing the uting the condensed refrigerant to the inlet ends of the several coils.

' EDWARD R, WOLFERT.

compressed refrigerant, and means for distrib- 

